Today, we're answering a question from listener Tim Smith, who asks: Why does anything exist?
To answer this, NHPR's Patrick McNamee King reached out to Nicole Gugliucci, an astrophysicist from Saint Anselm College.
To start, we have to look at baryons — the scientific term for "normal matter." As Gugliucci explains, this is "the stuff that makes up humans and planets and stars and galaxies, all the stuff we're used to."
But normal matter has a twin.
Mirror particles
You might be familiar with the concept of antimatter, which consists of particles that act like "mirror particles" to the matter we know. For example, where a normal electron is negatively charged, its antimatter counterpart is positively charged.
When these two worlds collide, things get explosive.
"Very famously — and this comes up in sci-fi very badly sometimes — the particle of matter meets its antimatter component," says Gugliucci. "They annihilate each other, creating a gamma-ray flash. And the particles are no more; it turns mass into energy."
We actually see these little tiny gamma-ray flashes in our own atmosphere when stray particles of antimatter interact with it, so we know it’s out there. But there isn't a lot of it, which brings us to a massive cosmic puzzle.
According to our current understanding of particle physics and the Big Bang, matter and antimatter should have been created in exactly equal amounts. If that had been the case, they would have completely annihilated one another long ago, leaving a universe of empty radiation.
"So the question is, why is there a little bit more of matter than antimatter?" Gugliucci says. "And we don't really know. It's kind of one of those big questions."
Could there be antimatter galaxies?
This raises another question: Is there a bunch of antimatter hiding out there in the deep cosmos that we just haven’t been able to detect yet?
"It's possible that whole antimatter galaxies could exist," Gugliucci notes. "They wouldn't look any different from matter galaxies to our telescopes."
However, if these massive cosmic pockets of antimatter were out there, they would eventually have to meet the regions of normal matter.
"At some point, there's going to be a boundary between the antimatter part and the matter part," Gugliucci explains. "We'd see a lot of gamma rays. We don't see that, but I don't think it's been ruled out."
For now, it remains one of the greatest unsolved mysteries of modern physics.
Thanks to Nicole Gugliucci for joining us, and thanks to Tim Smith for asking the question. If you have your own questions about the night sky, be sure to write to us Cosmic@nhpr.org.
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